Valley-contrasting Hall transport conventionally relies on the inversion symmetry breaking in two-dimensional systems, which greatly limits the selection range of valley materials. In particular, while monolayer transition metal dichalcogenides have been widely utilized as a well-known class of valley materials in valleytronics, the centrosymmetric nature hinders the realization of valley-contrasting properties in the bilayer counterparts. Here, taking ${\mathrm{MoS}}_2$ as an example, we discover valley-contrasting transport in bilayer transition metal dichalcogenides by exploring a nonlinear transport regime. Using effective models and first-principles calculations, our work demonstrates that nonvanishing nonlinear valley Hall conductivities emerge in a uniaxially strained ${\mathrm{MoS}}_2$ bilayer, owing to strain-induced band tilts of Dirac fermions. Compared with the valence bands, the conduction bands have smaller spin-orbit-coupling-induced band splittings and correspondingly they generate much more remarkable nonlinear valley Hall conductivity. Moreover, the nonlinear conductivities are highly tunable through modulating the strength and the direction of the strain, chemical potential, and interlayer gap. Our findings not only expand material choices for valleytronic applications, but also provides opportunities for designing advanced electronic devices that leverage nonlinear valley transports.

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• Hall effect
• Valleytronics
• Transition metal dichalcogenides
• Band structure methods
• Density functional calculations